DCA02MA029

A flight attendant was seriously injured when the airplane encountered turbulence while descending from flight level (FL) 350 to FL 340. Flight crew interview statements indicated that they were preparing for turbulence and that they wanted the passengers and flight attendants seated with their seatbelts fastened. However, the flight crew did not advise the lead flight attendant (LFA) of the turbulence level and its anticipated duration nor did they use turbulence codes, as stipulated in Northwest Airlines' Flight Operations Manual. The investigation also revealed that the LFA did not relay the turbulence information to all of the flight attendants, as stipulated in the company's Flight Attendant Manual.

Examination of the restraint system from the injured flight attendant's jump seat indicated that the restraint system did not fail during the turbulence upset. The Safety Board was unable to determine whether the lapbelt was improperly secured by the flight attendant or whether it was inadvertently disengaged during the turbulence upset.

The Safety Board's investigation examined the turbulence and the flight crew's operation of the airplane during the turbulence encounter to evaluate the effects on the airplane occupants. Analysis of the flight data recorder (FDR) data indicates that the turbulence caused substantial vertical and lateral oscillations, which may have made it difficult for the first officer (as the flying pilot) to maintain a constant pitch attitude.

The FDR data showed variations in the airplane's pitch attitude during the turbulence encounter. Despite the airplane's pitch excursions, statements from the flight crew indicate that they were attempting to maintain constant pitch attitudes during the turbulence upset. Nevertheless, FDR data indicate that the large and rapid pitch excursions were primarily a result of control column inputs made by the first officer. The Safety Board's investigation determined that the main pitchover (which likely caused the flight attendant's injuries) occurred as a result of the first officer's control inputs.

On March 22, 2002, about 0540 UTC, Northwest Airlines (NWA) flight 58, a McDonnell Douglas DC-10-30, N234NW, encountered turbulence while descending from flight level (FL) 350 to FL 340 approximately 30 degrees west longitude and one degree north of track "Sierra" (one of the designated North Atlantic air traffic routes for that day). Flight 58 was a regularly scheduled international passenger flight from Miami International Airport, Miami, Florida, to Amsterdam Schiphol Airport (AMS), Amsterdam, the Netherlands, with 251 passengers and 11 crewmembers on board. During the turbulence upset and recovery, a flight attendant seated in the rear of the airplane was seriously injured, and four passengers sustained minor injuries. The flight continued to Amsterdam and landed without further incident. The injured flight attendant and one of the injured passengers were transported to a hospital. The flight was operated under 14 Code of Federal Regulations Part 121 under an instrument flight plan.

History of flight

The captain provided a predeparture briefing to the lead flight attendant (LFA) during which he reviewed the standard operating procedures and stated that the flight crew would make the seatbelt announcements. He also provided the LFA with the flight route and weather information and told her that smooth conditions were expected once the flight was past Orlando, Florida. The predeparture captain/flight attendant briefing checklist indicated that no known turbulence was expected for the flight.

After takeoff, the seatbelt sign remained on until the flight had deviated around thunderstorms in the Orlando area. Once the flight got past the thunderstorms, it was smooth, and the flight attendants were allowed to begin meal service. The seatbelt sign was subsequently turned off, and it was not turned on again until the flight neared 32 degrees west longitude. At this time, the cabin was dark, and four of the eight flight attendants were on break.

At approximately 32 degrees west longitude (about 20 minutes before the turbulence upset), the flight began encountering light turbulence. At this point, the seatbelt sign was turned on, and the captain announced to the passengers that they needed to return to their seats and fasten their seatbelts.

The LFA and two of the other on-duty flight attendants walked through the cabin and checked the passengers' seatbelts. The flight attendants then took their seats and fastened their seatbelts. A few minutes later, the turbulence began increasing, and the LFA called the flight deck to find out how long the turbulence was expected to last. The second officer stated that the turbulence would be strong and asked if everyone was seated; the LFA responded, "yes."

As the flight approached 30 degrees west longitude, it began encountering moderate turbulence, and the captain told the second officer to tell the flight attendants to ensure that everyone was "down" and everything was put away. The second officer complied with the captain's instructions and asked the LFA to read back his directions; she complied. After numerous attempts to contact air traffic control (ATC) to request a lower altitude, ATC cleared the flight from FL 350 to FL 340.

As the flight began descending from FL 350, the airplane started to shake violently, to the point at which the captain could not read any of the instruments. The first officer stated that about 300 feet into the descent they got "walloped." The captain stated that the autopilot and throttles clicked off and that the airplane pitched up. He indicated that the worst turbulence occurred between FL 350 and FL 345 and that it was smooth once the flight reached FL 340.

Soon after the flight reached FL 340, the LFA called from the aft galley and reported that a flight attendant was seriously injured. A public address (PA) announcement was made requesting medical personnel, and several physicians responded to the aft galley. The injured flight attendant, who had been seated in position 4L (located on the left side of the airplane near the rear), told other crewmembers that her seatbelt "had not worked."

The captain declared an emergency and, subsequently, decided to continue to Amsterdam. After landing at AMS, medical personnel met the airplane. The injured flight attendant was removed and taken to a hospital.

Injuries to persons

Medical records and interviews indicated that the injured flight attendant sustained four broken vertebra and three broken ribs. She remained in a hospital in Amsterdam for several days before being transported back to the United States. Four passengers reported minor injuries.

Damage to airplane

A turbulence inspection performed after the flight found no structural damage. During the turbulence, two unstowed service carts in the aft galley were overturned, and various service items were dislodged from their stowed positions in the aft galley.

Personnel information

NWA records indicated that the captain had 13,267 hours company flight time, with 2,578 hours in the DC-10; the first officer had 8,279 hours company flight time, with 6,648 in the DC-10; and the second officer had 3,912 hours company flight time, with 31 hours in the DC-10. The accident flight was the second officer's first flight after his Initial Operating Experience on the DC-10 and his first flight with either of the other two pilots. The first officer had previously flown with the captain on both the DC-9 and the DC-10.

The LFA had worked for NWA for about 10 years. The accident flight was her first as LFA.

Flight crew interviews

Captain

The captain indicated that his PA announcement as the flight began encountering light turbulence was directed to the passengers. The captain stated that he did not use turbulence codes during his conversations with the flight attendants. (NWA uses turbulence codes to identify turbulence severity. Code 2 turbulence is described as "light or light/occasional-moderate turbulence"; code 4 turbulence is described as "moderate or moderate/occasional-severe turbulence"; and code 6 turbulence is described as "severe turbulence.")

The captain stated that his hand was on the glare shield before the turbulence upset and that when the turbulence caused his hand to slam down, it might have knocked the autothrottles off. The captain stated that a 1.6-G vertical shear caused the tail to whip as the first officer pitched the airplane's nose down. The captain stated that he assumed that the flight attendant and passenger injuries occurred when the first officer was pitching the airplane nose down because that was when the "biggest jolt hit."

The captain stated that the flight was smooth at FL 340 and that the worst turbulence lasted a minute or less. The captain also stated that he did not take over because the first officer was "doing just fine."

First Officer

The first officer indicated that although they heard on the radio that flights were increasingly being affected by turbulence about 100 miles to the south, there was no information about turbulence along their flightpath. He indicated that it was dark and that there was no horizon.

The first officer stated that he started to reduce the airspeed from about Mach .82 to about .80 as they began the descent from FL 350. Approximately 300 feet into the descent, he stated that they got "walloped" and that the autopilot clicked off. The first officer stated that he did not have his hands on the control yoke; instead, he was "guarding the controls" at the time the autopilot disconnected. The first officer stated that as soon as the autopilot disconnected and the airplane pitched down, he grabbed the yoke with both hands to keep the nose from pitching further down and to prevent the speed from building up. He stated that "the structural integrity of the airplane was a question in my mind." He also stated that he told the captain to cl